I. Field
The present invention relates generally to communication, and more specifically to techniques for receiving data in a wireless communication system.
II. Background
A wireless multiple-access communication system can concurrently communicate with multiple terminals on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. Multiple terminals may simultaneously transmit data on the reverse link and/or receive data on the forward link. This is often achieved by multiplexing the multiple data transmissions on each link to be orthogonal to one another in time, frequency and/or code domain. Complete orthogonality among the multiple data transmissions is typically not achieved in most instances due to various factors such as channel conditions, receiver imperfections, and so on. Nevertheless, the orthogonal multiplexing ensures that the data transmission for each terminal minimally interferes with the data transmissions for the other terminals.
In an orthogonal multiple-access system, the number of terminals that may communicate with a base station at any given moment is limited by the number of orthogonal dimensions available for data transmission. The number of available orthogonal dimensions may be determined by the number of available orthogonal codes in a code division multiple access (CDMA) system, the number of available frequency subbands in a frequency division multiple access (FDMA) system, or the number of available time slots in a time division multiple access (TDMA) system. In many instances, it is desirable to allow more terminals to simultaneously communicate with the base station in order to improve system capacity. However, if the number of communicating terminals exceeds the number of available orthogonal dimensions, then these terminals would interfere with one another, and the interference may degrade performance for all terminals.
There is therefore a need in the art for techniques to support simultaneous communication for more terminals in a multiple-access communication system.